The present invention relates to a tube for guiding a flexible pipe for transporting hydrocarbons, more commonly known as a guide tube.
The present invention is designed for offshore oil exploration and, more particularly, for surface offshore installations to which said flexible pipes are designed to be connected. These flexible pipes are of the type described in API (American Petroleum Institute) specifications 17J and 17B.
Known “J” guide tubes mounted vertically on an anchored floating support structure, for example, an oil platform, already make it possible to guide and to protect flexible pipes, one end of which is drawn on board the platform in order to be connected thereto.
Said guide tube comprises a lower tubular element that is generally submerged and has a substantially rectilinear section extending along an axis and extended by a free section having a curvature. This free section has an inner wall internal to the curvature against which said flexible pipe is fitted so as to be entrained in friction when entrained through said guide tube.
Furthermore, with a view to limiting the flexing of the flexible pipe in the vicinity of said free section, which could damage it, a bend limiter is fitted when said pipe is installed. This limiter consists of a bend stiffener made from flexible material, for example polyurethane, mounted fixedly on said free section and forming a sleeve surrounding the pipe in order to restrict its range of movement. A bend limiter of this type is described, in particular, in document FR 2 689 603.
A further embodiment disclosed in that document consists not in connecting the bend limiter directly to said free section, which is rigid, but in connecting it to a tubular member forming a sleeve that is mounted securely around the pipe, projecting and sliding in said free section. In this way, despite the low-level longitudinal movements of the flexible pipe in the guide tube, which gives rise to sliding of the tubular member in the free section, it remains secure and in the extension of said free section. Thus, the tubular member is held clear and the bend limiter extending it fulfills its role, just as in the preceding embodiment.
On the other hand, whereas in the installation method of the preceding embodiment, the flexible pipe was capable of being entrained longitudinally in friction in the bend limiter, in this latter embodiment this does not occur since the bend stiffener is mounted fixedly on the flexible pipe in terms of running length.
Nevertheless, in the two embodiments, the flexible pipe is likely to be entrained in friction against the internal inner wall inside the curvature of said free section, which risks damaging it.